diff options
Diffstat (limited to 'python/futures/concurrent')
| -rw-r--r-- | python/futures/concurrent/__init__.py | 3 | ||||
| -rw-r--r-- | python/futures/concurrent/futures/__init__.py | 23 | ||||
| -rw-r--r-- | python/futures/concurrent/futures/_base.py | 605 | ||||
| -rw-r--r-- | python/futures/concurrent/futures/process.py | 359 | ||||
| -rw-r--r-- | python/futures/concurrent/futures/thread.py | 134 |
5 files changed, 1124 insertions, 0 deletions
diff --git a/python/futures/concurrent/__init__.py b/python/futures/concurrent/__init__.py new file mode 100644 index 000000000..b36383a61 --- /dev/null +++ b/python/futures/concurrent/__init__.py @@ -0,0 +1,3 @@ +from pkgutil import extend_path + +__path__ = extend_path(__path__, __name__) diff --git a/python/futures/concurrent/futures/__init__.py b/python/futures/concurrent/futures/__init__.py new file mode 100644 index 000000000..428b14bdf --- /dev/null +++ b/python/futures/concurrent/futures/__init__.py @@ -0,0 +1,23 @@ +# Copyright 2009 Brian Quinlan. All Rights Reserved. +# Licensed to PSF under a Contributor Agreement. + +"""Execute computations asynchronously using threads or processes.""" + +__author__ = 'Brian Quinlan (brian@sweetapp.com)' + +from concurrent.futures._base import (FIRST_COMPLETED, + FIRST_EXCEPTION, + ALL_COMPLETED, + CancelledError, + TimeoutError, + Future, + Executor, + wait, + as_completed) +from concurrent.futures.thread import ThreadPoolExecutor + +try: + from concurrent.futures.process import ProcessPoolExecutor +except ImportError: + # some platforms don't have multiprocessing + pass diff --git a/python/futures/concurrent/futures/_base.py b/python/futures/concurrent/futures/_base.py new file mode 100644 index 000000000..fbf027512 --- /dev/null +++ b/python/futures/concurrent/futures/_base.py @@ -0,0 +1,605 @@ +# Copyright 2009 Brian Quinlan. All Rights Reserved. +# Licensed to PSF under a Contributor Agreement. + +import collections +import logging +import threading +import itertools +import time + +__author__ = 'Brian Quinlan (brian@sweetapp.com)' + +FIRST_COMPLETED = 'FIRST_COMPLETED' +FIRST_EXCEPTION = 'FIRST_EXCEPTION' +ALL_COMPLETED = 'ALL_COMPLETED' +_AS_COMPLETED = '_AS_COMPLETED' + +# Possible future states (for internal use by the futures package). +PENDING = 'PENDING' +RUNNING = 'RUNNING' +# The future was cancelled by the user... +CANCELLED = 'CANCELLED' +# ...and _Waiter.add_cancelled() was called by a worker. +CANCELLED_AND_NOTIFIED = 'CANCELLED_AND_NOTIFIED' +FINISHED = 'FINISHED' + +_FUTURE_STATES = [ + PENDING, + RUNNING, + CANCELLED, + CANCELLED_AND_NOTIFIED, + FINISHED +] + +_STATE_TO_DESCRIPTION_MAP = { + PENDING: "pending", + RUNNING: "running", + CANCELLED: "cancelled", + CANCELLED_AND_NOTIFIED: "cancelled", + FINISHED: "finished" +} + +# Logger for internal use by the futures package. +LOGGER = logging.getLogger("concurrent.futures") + +class Error(Exception): + """Base class for all future-related exceptions.""" + pass + +class CancelledError(Error): + """The Future was cancelled.""" + pass + +class TimeoutError(Error): + """The operation exceeded the given deadline.""" + pass + +class _Waiter(object): + """Provides the event that wait() and as_completed() block on.""" + def __init__(self): + self.event = threading.Event() + self.finished_futures = [] + + def add_result(self, future): + self.finished_futures.append(future) + + def add_exception(self, future): + self.finished_futures.append(future) + + def add_cancelled(self, future): + self.finished_futures.append(future) + +class _AsCompletedWaiter(_Waiter): + """Used by as_completed().""" + + def __init__(self): + super(_AsCompletedWaiter, self).__init__() + self.lock = threading.Lock() + + def add_result(self, future): + with self.lock: + super(_AsCompletedWaiter, self).add_result(future) + self.event.set() + + def add_exception(self, future): + with self.lock: + super(_AsCompletedWaiter, self).add_exception(future) + self.event.set() + + def add_cancelled(self, future): + with self.lock: + super(_AsCompletedWaiter, self).add_cancelled(future) + self.event.set() + +class _FirstCompletedWaiter(_Waiter): + """Used by wait(return_when=FIRST_COMPLETED).""" + + def add_result(self, future): + super(_FirstCompletedWaiter, self).add_result(future) + self.event.set() + + def add_exception(self, future): + super(_FirstCompletedWaiter, self).add_exception(future) + self.event.set() + + def add_cancelled(self, future): + super(_FirstCompletedWaiter, self).add_cancelled(future) + self.event.set() + +class _AllCompletedWaiter(_Waiter): + """Used by wait(return_when=FIRST_EXCEPTION and ALL_COMPLETED).""" + + def __init__(self, num_pending_calls, stop_on_exception): + self.num_pending_calls = num_pending_calls + self.stop_on_exception = stop_on_exception + self.lock = threading.Lock() + super(_AllCompletedWaiter, self).__init__() + + def _decrement_pending_calls(self): + with self.lock: + self.num_pending_calls -= 1 + if not self.num_pending_calls: + self.event.set() + + def add_result(self, future): + super(_AllCompletedWaiter, self).add_result(future) + self._decrement_pending_calls() + + def add_exception(self, future): + super(_AllCompletedWaiter, self).add_exception(future) + if self.stop_on_exception: + self.event.set() + else: + self._decrement_pending_calls() + + def add_cancelled(self, future): + super(_AllCompletedWaiter, self).add_cancelled(future) + self._decrement_pending_calls() + +class _AcquireFutures(object): + """A context manager that does an ordered acquire of Future conditions.""" + + def __init__(self, futures): + self.futures = sorted(futures, key=id) + + def __enter__(self): + for future in self.futures: + future._condition.acquire() + + def __exit__(self, *args): + for future in self.futures: + future._condition.release() + +def _create_and_install_waiters(fs, return_when): + if return_when == _AS_COMPLETED: + waiter = _AsCompletedWaiter() + elif return_when == FIRST_COMPLETED: + waiter = _FirstCompletedWaiter() + else: + pending_count = sum( + f._state not in [CANCELLED_AND_NOTIFIED, FINISHED] for f in fs) + + if return_when == FIRST_EXCEPTION: + waiter = _AllCompletedWaiter(pending_count, stop_on_exception=True) + elif return_when == ALL_COMPLETED: + waiter = _AllCompletedWaiter(pending_count, stop_on_exception=False) + else: + raise ValueError("Invalid return condition: %r" % return_when) + + for f in fs: + f._waiters.append(waiter) + + return waiter + +def as_completed(fs, timeout=None): + """An iterator over the given futures that yields each as it completes. + + Args: + fs: The sequence of Futures (possibly created by different Executors) to + iterate over. + timeout: The maximum number of seconds to wait. If None, then there + is no limit on the wait time. + + Returns: + An iterator that yields the given Futures as they complete (finished or + cancelled). If any given Futures are duplicated, they will be returned + once. + + Raises: + TimeoutError: If the entire result iterator could not be generated + before the given timeout. + """ + if timeout is not None: + end_time = timeout + time.time() + + fs = set(fs) + with _AcquireFutures(fs): + finished = set( + f for f in fs + if f._state in [CANCELLED_AND_NOTIFIED, FINISHED]) + pending = fs - finished + waiter = _create_and_install_waiters(fs, _AS_COMPLETED) + + try: + for future in finished: + yield future + + while pending: + if timeout is None: + wait_timeout = None + else: + wait_timeout = end_time - time.time() + if wait_timeout < 0: + raise TimeoutError( + '%d (of %d) futures unfinished' % ( + len(pending), len(fs))) + + waiter.event.wait(wait_timeout) + + with waiter.lock: + finished = waiter.finished_futures + waiter.finished_futures = [] + waiter.event.clear() + + for future in finished: + yield future + pending.remove(future) + + finally: + for f in fs: + f._waiters.remove(waiter) + +DoneAndNotDoneFutures = collections.namedtuple( + 'DoneAndNotDoneFutures', 'done not_done') +def wait(fs, timeout=None, return_when=ALL_COMPLETED): + """Wait for the futures in the given sequence to complete. + + Args: + fs: The sequence of Futures (possibly created by different Executors) to + wait upon. + timeout: The maximum number of seconds to wait. If None, then there + is no limit on the wait time. + return_when: Indicates when this function should return. The options + are: + + FIRST_COMPLETED - Return when any future finishes or is + cancelled. + FIRST_EXCEPTION - Return when any future finishes by raising an + exception. If no future raises an exception + then it is equivalent to ALL_COMPLETED. + ALL_COMPLETED - Return when all futures finish or are cancelled. + + Returns: + A named 2-tuple of sets. The first set, named 'done', contains the + futures that completed (is finished or cancelled) before the wait + completed. The second set, named 'not_done', contains uncompleted + futures. + """ + with _AcquireFutures(fs): + done = set(f for f in fs + if f._state in [CANCELLED_AND_NOTIFIED, FINISHED]) + not_done = set(fs) - done + + if (return_when == FIRST_COMPLETED) and done: + return DoneAndNotDoneFutures(done, not_done) + elif (return_when == FIRST_EXCEPTION) and done: + if any(f for f in done + if not f.cancelled() and f.exception() is not None): + return DoneAndNotDoneFutures(done, not_done) + + if len(done) == len(fs): + return DoneAndNotDoneFutures(done, not_done) + + waiter = _create_and_install_waiters(fs, return_when) + + waiter.event.wait(timeout) + for f in fs: + f._waiters.remove(waiter) + + done.update(waiter.finished_futures) + return DoneAndNotDoneFutures(done, set(fs) - done) + +class Future(object): + """Represents the result of an asynchronous computation.""" + + def __init__(self): + """Initializes the future. Should not be called by clients.""" + self._condition = threading.Condition() + self._state = PENDING + self._result = None + self._exception = None + self._traceback = None + self._waiters = [] + self._done_callbacks = [] + + def _invoke_callbacks(self): + for callback in self._done_callbacks: + try: + callback(self) + except Exception: + LOGGER.exception('exception calling callback for %r', self) + + def __repr__(self): + with self._condition: + if self._state == FINISHED: + if self._exception: + return '<Future at %s state=%s raised %s>' % ( + hex(id(self)), + _STATE_TO_DESCRIPTION_MAP[self._state], + self._exception.__class__.__name__) + else: + return '<Future at %s state=%s returned %s>' % ( + hex(id(self)), + _STATE_TO_DESCRIPTION_MAP[self._state], + self._result.__class__.__name__) + return '<Future at %s state=%s>' % ( + hex(id(self)), + _STATE_TO_DESCRIPTION_MAP[self._state]) + + def cancel(self): + """Cancel the future if possible. + + Returns True if the future was cancelled, False otherwise. A future + cannot be cancelled if it is running or has already completed. + """ + with self._condition: + if self._state in [RUNNING, FINISHED]: + return False + + if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]: + return True + + self._state = CANCELLED + self._condition.notify_all() + + self._invoke_callbacks() + return True + + def cancelled(self): + """Return True if the future has cancelled.""" + with self._condition: + return self._state in [CANCELLED, CANCELLED_AND_NOTIFIED] + + def running(self): + """Return True if the future is currently executing.""" + with self._condition: + return self._state == RUNNING + + def done(self): + """Return True of the future was cancelled or finished executing.""" + with self._condition: + return self._state in [CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED] + + def __get_result(self): + if self._exception: + raise type(self._exception), self._exception, self._traceback + else: + return self._result + + def add_done_callback(self, fn): + """Attaches a callable that will be called when the future finishes. + + Args: + fn: A callable that will be called with this future as its only + argument when the future completes or is cancelled. The callable + will always be called by a thread in the same process in which + it was added. If the future has already completed or been + cancelled then the callable will be called immediately. These + callables are called in the order that they were added. + """ + with self._condition: + if self._state not in [CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED]: + self._done_callbacks.append(fn) + return + fn(self) + + def result(self, timeout=None): + """Return the result of the call that the future represents. + + Args: + timeout: The number of seconds to wait for the result if the future + isn't done. If None, then there is no limit on the wait time. + + Returns: + The result of the call that the future represents. + + Raises: + CancelledError: If the future was cancelled. + TimeoutError: If the future didn't finish executing before the given + timeout. + Exception: If the call raised then that exception will be raised. + """ + with self._condition: + if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]: + raise CancelledError() + elif self._state == FINISHED: + return self.__get_result() + + self._condition.wait(timeout) + + if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]: + raise CancelledError() + elif self._state == FINISHED: + return self.__get_result() + else: + raise TimeoutError() + + def exception_info(self, timeout=None): + """Return a tuple of (exception, traceback) raised by the call that the + future represents. + + Args: + timeout: The number of seconds to wait for the exception if the + future isn't done. If None, then there is no limit on the wait + time. + + Returns: + The exception raised by the call that the future represents or None + if the call completed without raising. + + Raises: + CancelledError: If the future was cancelled. + TimeoutError: If the future didn't finish executing before the given + timeout. + """ + with self._condition: + if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]: + raise CancelledError() + elif self._state == FINISHED: + return self._exception, self._traceback + + self._condition.wait(timeout) + + if self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]: + raise CancelledError() + elif self._state == FINISHED: + return self._exception, self._traceback + else: + raise TimeoutError() + + def exception(self, timeout=None): + """Return the exception raised by the call that the future represents. + + Args: + timeout: The number of seconds to wait for the exception if the + future isn't done. If None, then there is no limit on the wait + time. + + Returns: + The exception raised by the call that the future represents or None + if the call completed without raising. + + Raises: + CancelledError: If the future was cancelled. + TimeoutError: If the future didn't finish executing before the given + timeout. + """ + return self.exception_info(timeout)[0] + + # The following methods should only be used by Executors and in tests. + def set_running_or_notify_cancel(self): + """Mark the future as running or process any cancel notifications. + + Should only be used by Executor implementations and unit tests. + + If the future has been cancelled (cancel() was called and returned + True) then any threads waiting on the future completing (though calls + to as_completed() or wait()) are notified and False is returned. + + If the future was not cancelled then it is put in the running state + (future calls to running() will return True) and True is returned. + + This method should be called by Executor implementations before + executing the work associated with this future. If this method returns + False then the work should not be executed. + + Returns: + False if the Future was cancelled, True otherwise. + + Raises: + RuntimeError: if this method was already called or if set_result() + or set_exception() was called. + """ + with self._condition: + if self._state == CANCELLED: + self._state = CANCELLED_AND_NOTIFIED + for waiter in self._waiters: + waiter.add_cancelled(self) + # self._condition.notify_all() is not necessary because + # self.cancel() triggers a notification. + return False + elif self._state == PENDING: + self._state = RUNNING + return True + else: + LOGGER.critical('Future %s in unexpected state: %s', + id(self), + self._state) + raise RuntimeError('Future in unexpected state') + + def set_result(self, result): + """Sets the return value of work associated with the future. + + Should only be used by Executor implementations and unit tests. + """ + with self._condition: + self._result = result + self._state = FINISHED + for waiter in self._waiters: + waiter.add_result(self) + self._condition.notify_all() + self._invoke_callbacks() + + def set_exception_info(self, exception, traceback): + """Sets the result of the future as being the given exception + and traceback. + + Should only be used by Executor implementations and unit tests. + """ + with self._condition: + self._exception = exception + self._traceback = traceback + self._state = FINISHED + for waiter in self._waiters: + waiter.add_exception(self) + self._condition.notify_all() + self._invoke_callbacks() + + def set_exception(self, exception): + """Sets the result of the future as being the given exception. + + Should only be used by Executor implementations and unit tests. + """ + self.set_exception_info(exception, None) + +class Executor(object): + """This is an abstract base class for concrete asynchronous executors.""" + + def submit(self, fn, *args, **kwargs): + """Submits a callable to be executed with the given arguments. + + Schedules the callable to be executed as fn(*args, **kwargs) and returns + a Future instance representing the execution of the callable. + + Returns: + A Future representing the given call. + """ + raise NotImplementedError() + + def map(self, fn, *iterables, **kwargs): + """Returns a iterator equivalent to map(fn, iter). + + Args: + fn: A callable that will take as many arguments as there are + passed iterables. + timeout: The maximum number of seconds to wait. If None, then there + is no limit on the wait time. + + Returns: + An iterator equivalent to: map(func, *iterables) but the calls may + be evaluated out-of-order. + + Raises: + TimeoutError: If the entire result iterator could not be generated + before the given timeout. + Exception: If fn(*args) raises for any values. + """ + timeout = kwargs.get('timeout') + if timeout is not None: + end_time = timeout + time.time() + + fs = [self.submit(fn, *args) for args in itertools.izip(*iterables)] + + # Yield must be hidden in closure so that the futures are submitted + # before the first iterator value is required. + def result_iterator(): + try: + for future in fs: + if timeout is None: + yield future.result() + else: + yield future.result(end_time - time.time()) + finally: + for future in fs: + future.cancel() + return result_iterator() + + def shutdown(self, wait=True): + """Clean-up the resources associated with the Executor. + + It is safe to call this method several times. Otherwise, no other + methods can be called after this one. + + Args: + wait: If True then shutdown will not return until all running + futures have finished executing and the resources used by the + executor have been reclaimed. + """ + pass + + def __enter__(self): + return self + + def __exit__(self, exc_type, exc_val, exc_tb): + self.shutdown(wait=True) + return False diff --git a/python/futures/concurrent/futures/process.py b/python/futures/concurrent/futures/process.py new file mode 100644 index 000000000..ee463f181 --- /dev/null +++ b/python/futures/concurrent/futures/process.py @@ -0,0 +1,359 @@ +# Copyright 2009 Brian Quinlan. All Rights Reserved. +# Licensed to PSF under a Contributor Agreement. + +"""Implements ProcessPoolExecutor. + +The follow diagram and text describe the data-flow through the system: + +|======================= In-process =====================|== Out-of-process ==| + ++----------+ +----------+ +--------+ +-----------+ +---------+ +| | => | Work Ids | => | | => | Call Q | => | | +| | +----------+ | | +-----------+ | | +| | | ... | | | | ... | | | +| | | 6 | | | | 5, call() | | | +| | | 7 | | | | ... | | | +| Process | | ... | | Local | +-----------+ | Process | +| Pool | +----------+ | Worker | | #1..n | +| Executor | | Thread | | | +| | +----------- + | | +-----------+ | | +| | <=> | Work Items | <=> | | <= | Result Q | <= | | +| | +------------+ | | +-----------+ | | +| | | 6: call() | | | | ... | | | +| | | future | | | | 4, result | | | +| | | ... | | | | 3, except | | | ++----------+ +------------+ +--------+ +-----------+ +---------+ + +Executor.submit() called: +- creates a uniquely numbered _WorkItem and adds it to the "Work Items" dict +- adds the id of the _WorkItem to the "Work Ids" queue + +Local worker thread: +- reads work ids from the "Work Ids" queue and looks up the corresponding + WorkItem from the "Work Items" dict: if the work item has been cancelled then + it is simply removed from the dict, otherwise it is repackaged as a + _CallItem and put in the "Call Q". New _CallItems are put in the "Call Q" + until "Call Q" is full. NOTE: the size of the "Call Q" is kept small because + calls placed in the "Call Q" can no longer be cancelled with Future.cancel(). +- reads _ResultItems from "Result Q", updates the future stored in the + "Work Items" dict and deletes the dict entry + +Process #1..n: +- reads _CallItems from "Call Q", executes the calls, and puts the resulting + _ResultItems in "Request Q" +""" + +import atexit +from concurrent.futures import _base +import Queue as queue +import multiprocessing +import threading +import weakref +import sys + +__author__ = 'Brian Quinlan (brian@sweetapp.com)' + +# Workers are created as daemon threads and processes. This is done to allow the +# interpreter to exit when there are still idle processes in a +# ProcessPoolExecutor's process pool (i.e. shutdown() was not called). However, +# allowing workers to die with the interpreter has two undesirable properties: +# - The workers would still be running during interpretor shutdown, +# meaning that they would fail in unpredictable ways. +# - The workers could be killed while evaluating a work item, which could +# be bad if the callable being evaluated has external side-effects e.g. +# writing to a file. +# +# To work around this problem, an exit handler is installed which tells the +# workers to exit when their work queues are empty and then waits until the +# threads/processes finish. + +_threads_queues = weakref.WeakKeyDictionary() +_shutdown = False + +def _python_exit(): + global _shutdown + _shutdown = True + items = list(_threads_queues.items()) + for t, q in items: + q.put(None) + for t, q in items: + t.join() + +# Controls how many more calls than processes will be queued in the call queue. +# A smaller number will mean that processes spend more time idle waiting for +# work while a larger number will make Future.cancel() succeed less frequently +# (Futures in the call queue cannot be cancelled). +EXTRA_QUEUED_CALLS = 1 + +class _WorkItem(object): + def __init__(self, future, fn, args, kwargs): + self.future = future + self.fn = fn + self.args = args + self.kwargs = kwargs + +class _ResultItem(object): + def __init__(self, work_id, exception=None, result=None): + self.work_id = work_id + self.exception = exception + self.result = result + +class _CallItem(object): + def __init__(self, work_id, fn, args, kwargs): + self.work_id = work_id + self.fn = fn + self.args = args + self.kwargs = kwargs + +def _process_worker(call_queue, result_queue): + """Evaluates calls from call_queue and places the results in result_queue. + + This worker is run in a separate process. + + Args: + call_queue: A multiprocessing.Queue of _CallItems that will be read and + evaluated by the worker. + result_queue: A multiprocessing.Queue of _ResultItems that will written + to by the worker. + shutdown: A multiprocessing.Event that will be set as a signal to the + worker that it should exit when call_queue is empty. + """ + while True: + call_item = call_queue.get(block=True) + if call_item is None: + # Wake up queue management thread + result_queue.put(None) + return + try: + r = call_item.fn(*call_item.args, **call_item.kwargs) + except BaseException: + e = sys.exc_info()[1] + result_queue.put(_ResultItem(call_item.work_id, + exception=e)) + else: + result_queue.put(_ResultItem(call_item.work_id, + result=r)) + +def _add_call_item_to_queue(pending_work_items, + work_ids, + call_queue): + """Fills call_queue with _WorkItems from pending_work_items. + + This function never blocks. + + Args: + pending_work_items: A dict mapping work ids to _WorkItems e.g. + {5: <_WorkItem...>, 6: <_WorkItem...>, ...} + work_ids: A queue.Queue of work ids e.g. Queue([5, 6, ...]). Work ids + are consumed and the corresponding _WorkItems from + pending_work_items are transformed into _CallItems and put in + call_queue. + call_queue: A multiprocessing.Queue that will be filled with _CallItems + derived from _WorkItems. + """ + while True: + if call_queue.full(): + return + try: + work_id = work_ids.get(block=False) + except queue.Empty: + return + else: + work_item = pending_work_items[work_id] + + if work_item.future.set_running_or_notify_cancel(): + call_queue.put(_CallItem(work_id, + work_item.fn, + work_item.args, + work_item.kwargs), + block=True) + else: + del pending_work_items[work_id] + continue + +def _queue_management_worker(executor_reference, + processes, + pending_work_items, + work_ids_queue, + call_queue, + result_queue): + """Manages the communication between this process and the worker processes. + + This function is run in a local thread. + + Args: + executor_reference: A weakref.ref to the ProcessPoolExecutor that owns + this thread. Used to determine if the ProcessPoolExecutor has been + garbage collected and that this function can exit. + process: A list of the multiprocessing.Process instances used as + workers. + pending_work_items: A dict mapping work ids to _WorkItems e.g. + {5: <_WorkItem...>, 6: <_WorkItem...>, ...} + work_ids_queue: A queue.Queue of work ids e.g. Queue([5, 6, ...]). + call_queue: A multiprocessing.Queue that will be filled with _CallItems + derived from _WorkItems for processing by the process workers. + result_queue: A multiprocessing.Queue of _ResultItems generated by the + process workers. + """ + nb_shutdown_processes = [0] + def shutdown_one_process(): + """Tell a worker to terminate, which will in turn wake us again""" + call_queue.put(None) + nb_shutdown_processes[0] += 1 + while True: + _add_call_item_to_queue(pending_work_items, + work_ids_queue, + call_queue) + + result_item = result_queue.get(block=True) + if result_item is not None: + work_item = pending_work_items[result_item.work_id] + del pending_work_items[result_item.work_id] + + if result_item.exception: + work_item.future.set_exception(result_item.exception) + else: + work_item.future.set_result(result_item.result) + # Delete references to object. See issue16284 + del work_item + # Check whether we should start shutting down. + executor = executor_reference() + # No more work items can be added if: + # - The interpreter is shutting down OR + # - The executor that owns this worker has been collected OR + # - The executor that owns this worker has been shutdown. + if _shutdown or executor is None or executor._shutdown_thread: + # Since no new work items can be added, it is safe to shutdown + # this thread if there are no pending work items. + if not pending_work_items: + while nb_shutdown_processes[0] < len(processes): + shutdown_one_process() + # If .join() is not called on the created processes then + # some multiprocessing.Queue methods may deadlock on Mac OS + # X. + for p in processes: + p.join() + call_queue.close() + return + del executor + +_system_limits_checked = False +_system_limited = None +def _check_system_limits(): + global _system_limits_checked, _system_limited + if _system_limits_checked: + if _system_limited: + raise NotImplementedError(_system_limited) + _system_limits_checked = True + try: + import os + nsems_max = os.sysconf("SC_SEM_NSEMS_MAX") + except (AttributeError, ValueError): + # sysconf not available or setting not available + return + if nsems_max == -1: + # indetermine limit, assume that limit is determined + # by available memory only + return + if nsems_max >= 256: + # minimum number of semaphores available + # according to POSIX + return + _system_limited = "system provides too few semaphores (%d available, 256 necessary)" % nsems_max + raise NotImplementedError(_system_limited) + +class ProcessPoolExecutor(_base.Executor): + def __init__(self, max_workers=None): + """Initializes a new ProcessPoolExecutor instance. + + Args: + max_workers: The maximum number of processes that can be used to + execute the given calls. If None or not given then as many + worker processes will be created as the machine has processors. + """ + _check_system_limits() + + if max_workers is None: + self._max_workers = multiprocessing.cpu_count() + else: + self._max_workers = max_workers + + # Make the call queue slightly larger than the number of processes to + # prevent the worker processes from idling. But don't make it too big + # because futures in the call queue cannot be cancelled. + self._call_queue = multiprocessing.Queue(self._max_workers + + EXTRA_QUEUED_CALLS) + self._result_queue = multiprocessing.Queue() + self._work_ids = queue.Queue() + self._queue_management_thread = None + self._processes = set() + + # Shutdown is a two-step process. + self._shutdown_thread = False + self._shutdown_lock = threading.Lock() + self._queue_count = 0 + self._pending_work_items = {} + + def _start_queue_management_thread(self): + # When the executor gets lost, the weakref callback will wake up + # the queue management thread. + def weakref_cb(_, q=self._result_queue): + q.put(None) + if self._queue_management_thread is None: + self._queue_management_thread = threading.Thread( + target=_queue_management_worker, + args=(weakref.ref(self, weakref_cb), + self._processes, + self._pending_work_items, + self._work_ids, + self._call_queue, + self._result_queue)) + self._queue_management_thread.daemon = True + self._queue_management_thread.start() + _threads_queues[self._queue_management_thread] = self._result_queue + + def _adjust_process_count(self): + for _ in range(len(self._processes), self._max_workers): + p = multiprocessing.Process( + target=_process_worker, + args=(self._call_queue, + self._result_queue)) + p.start() + self._processes.add(p) + + def submit(self, fn, *args, **kwargs): + with self._shutdown_lock: + if self._shutdown_thread: + raise RuntimeError('cannot schedule new futures after shutdown') + + f = _base.Future() + w = _WorkItem(f, fn, args, kwargs) + + self._pending_work_items[self._queue_count] = w + self._work_ids.put(self._queue_count) + self._queue_count += 1 + # Wake up queue management thread + self._result_queue.put(None) + + self._start_queue_management_thread() + self._adjust_process_count() + return f + submit.__doc__ = _base.Executor.submit.__doc__ + + def shutdown(self, wait=True): + with self._shutdown_lock: + self._shutdown_thread = True + if self._queue_management_thread: + # Wake up queue management thread + self._result_queue.put(None) + if wait: + self._queue_management_thread.join() + # To reduce the risk of openning too many files, remove references to + # objects that use file descriptors. + self._queue_management_thread = None + self._call_queue = None + self._result_queue = None + self._processes = None + shutdown.__doc__ = _base.Executor.shutdown.__doc__ + +atexit.register(_python_exit) diff --git a/python/futures/concurrent/futures/thread.py b/python/futures/concurrent/futures/thread.py new file mode 100644 index 000000000..fa5ed0c09 --- /dev/null +++ b/python/futures/concurrent/futures/thread.py @@ -0,0 +1,134 @@ +# Copyright 2009 Brian Quinlan. All Rights Reserved. +# Licensed to PSF under a Contributor Agreement. + +"""Implements ThreadPoolExecutor.""" + +import atexit +from concurrent.futures import _base +import Queue as queue +import threading +import weakref +import sys + +__author__ = 'Brian Quinlan (brian@sweetapp.com)' + +# Workers are created as daemon threads. This is done to allow the interpreter +# to exit when there are still idle threads in a ThreadPoolExecutor's thread +# pool (i.e. shutdown() was not called). However, allowing workers to die with +# the interpreter has two undesirable properties: +# - The workers would still be running during interpretor shutdown, +# meaning that they would fail in unpredictable ways. +# - The workers could be killed while evaluating a work item, which could +# be bad if the callable being evaluated has external side-effects e.g. +# writing to a file. +# +# To work around this problem, an exit handler is installed which tells the +# workers to exit when their work queues are empty and then waits until the +# threads finish. + +_threads_queues = weakref.WeakKeyDictionary() +_shutdown = False + +def _python_exit(): + global _shutdown + _shutdown = True + items = list(_threads_queues.items()) + for t, q in items: + q.put(None) + for t, q in items: + t.join() + +atexit.register(_python_exit) + +class _WorkItem(object): + def __init__(self, future, fn, args, kwargs): + self.future = future + self.fn = fn + self.args = args + self.kwargs = kwargs + + def run(self): + if not self.future.set_running_or_notify_cancel(): + return + + try: + result = self.fn(*self.args, **self.kwargs) + except BaseException: + e, tb = sys.exc_info()[1:] + self.future.set_exception_info(e, tb) + else: + self.future.set_result(result) + +def _worker(executor_reference, work_queue): + try: + while True: + work_item = work_queue.get(block=True) + if work_item is not None: + work_item.run() + # Delete references to object. See issue16284 + del work_item + continue + executor = executor_reference() + # Exit if: + # - The interpreter is shutting down OR + # - The executor that owns the worker has been collected OR + # - The executor that owns the worker has been shutdown. + if _shutdown or executor is None or executor._shutdown: + # Notice other workers + work_queue.put(None) + return + del executor + except BaseException: + _base.LOGGER.critical('Exception in worker', exc_info=True) + +class ThreadPoolExecutor(_base.Executor): + def __init__(self, max_workers): + """Initializes a new ThreadPoolExecutor instance. + + Args: + max_workers: The maximum number of threads that can be used to + execute the given calls. + """ + self._max_workers = max_workers + self._work_queue = queue.Queue() + self._threads = set() + self._shutdown = False + self._shutdown_lock = threading.Lock() + + def submit(self, fn, *args, **kwargs): + with self._shutdown_lock: + if self._shutdown: + raise RuntimeError('cannot schedule new futures after shutdown') + + f = _base.Future() + w = _WorkItem(f, fn, args, kwargs) + + self._work_queue.put(w) + self._adjust_thread_count() + return f + submit.__doc__ = _base.Executor.submit.__doc__ + + def _adjust_thread_count(self): + # When the executor gets lost, the weakref callback will wake up + # the worker threads. + def weakref_cb(_, q=self._work_queue): + q.put(None) + # TODO(bquinlan): Should avoid creating new threads if there are more + # idle threads than items in the work queue. + if len(self._threads) < self._max_workers: + t = threading.Thread(target=_worker, + args=(weakref.ref(self, weakref_cb), + self._work_queue)) + t.daemon = True + t.start() + self._threads.add(t) + _threads_queues[t] = self._work_queue + + def shutdown(self, wait=True): + with self._shutdown_lock: + self._shutdown = True + self._work_queue.put(None) + if wait: + for t in self._threads: + t.join() + shutdown.__doc__ = _base.Executor.shutdown.__doc__ |